Oil burner baffle system



p 22, 1953 K. -s. JENSON HAL 2,652,889

OIL BURNER BAFFLE SYSTEM Filed Oct. 22, 1948 2 Sheets-Sheet l INVENTORS Kenneth S. Jensen By Frederick IM Suhr P 1953 K. s. JENSON ETAL 2,652,889

OIL BURNER BAFFLE SYSTEM Filed Oct. 22, 1948 2 Sheets -Sheet 2 INVENTORS Kenne th $.Jenson Fredenck I44 50hr Patented Sept. 22, 1953 OILBURNER BAFFLE SYSTEM Kenneth S Jensen and Frederick W. Suhr, Wis-- consin Rapids, Wis., assignors to Preway Inc.,

lscolisin consin' Rapids, Wis., a-corporation of Wis- Application bctober 22, 1948, Serial No. 55,956

This invention relates to a, system of bafiles de- 10 Claims; (Cl. 158-91) signed for 'usewith a liquidlfuelvaporizing pot type "burner. The present improvements are concerned primarily with the baffle structure per S8. g V

Pot typ burners forvapori'zed liquid fuel operate normally with a flame "which burns from and over africhmixture of oil vapor and airwhich V Properioperation reis present inside the pot.

quires'th a t the vapor atmosphere be of such richness thatf igni'tion cannot take place except in the areawhereair is'in'jectedin sufficient quantity. Theburhing rate is controlled by varying the supply o'fliquid fuel. As more or less'fuel is released into the burner, the depth of fuel vapor is raised or'lowered; "thebase of the' fiame is likewise ra'i se'd and lowered according'to the depth of the fuellvapor. If the fuel control means be set to' supnlya minimum or low "fire volume of fuel, anyied'uc'tion in the' fuel supply below that pointwill'lduce the richness of the fuel vapor atmosphere to such an extent that improper V control means which operates irrespective of the u creased beyond that where horizontal plates lose their effectiveness; for the rising gas a' uniform vertical spacing betweensegmental bafiies by providing a tortuous passage from stage to stage between the bafiles; means to insure a gradual rise g of the flame from zone to zone without noticeably combustioi'rwill'take place and produce 'a smoky fiam 'whi'chburns directly the oil 'pool on' the burner bottom.

In most instances it is'found that more heat fromthe' surface of than is desired is givcn'oif at the minimum or propervolumeof fuel supply; Toreduce excessive heat in such conditions" a reduction of air supply-andvolume of fuel vapor atmosphere must be made? 'Inthe past this reduction "-of' air and volume'of fuelvapor atmosphere has been aocoin- I plished in various ways; but'always with a reduction in burner performance. 1

'One'of the objects of our invention is to provide a burner .having' a wide range ofcombustion' stages varying from a Very small fire 'to an extremely'large-fire with a high degree of combustion efficiencymaintained over the entire range. Another object is to provide means for guiding the combustible-"gas mixture in and about the burneruniformly prior-to and during its combustion. Another object isto' provide means for facilitating expansion and contraction of the fuel vapor atmosphere as more or less liquid fuel is supplied: to the burner. Another object .is to provide a pot: type burner for vaporized liquid fuel in which these several objects are attained but with means to prevent air eddies from developing on one side-of the burner, te ding to cause the flameitodecentralize and smoke.

Other; objects attained bythis invention include the provision of an elongated fixed passageway for th rising burnable gas mixture; control of the rising burnable gas mixture vertically even where'the distance between baflle plates is inchanging its general shape or character; 'a fixed passageway for the rising burnable gas mixture separate and distinct "from a vertical opening which is provided centrally through the burner; a bafile structure which can be readily removed through a small heat drum door opening whenever repairs or cleaning are to be attended to; a

battle structure which will increase the heat output of the burner over that which is obtainable without such bafiles; means for increasing the carbon dioxide percentage of the flue products at the maximum fire; bafile means which will permit reflected heat from above the flame to readily vaporize the fuel therebelow on the burner bottom; means to facilitate vaporizing and consumption of stable hydrocarbons, such as catalytically 'crackedl fuel oil, without excessive accumulations of soot or carbon'residue in the burner, or

in the associated heat drum or flues; a bafile structure which is so designed as to prevent excessive warpage and sagging of any of its parts due to the intense heat present in the burner pot; and means for releasably uniting the baflle structure together in two half sections so that they can easily be separated for removal from or replacement-within the pot burner without getting out of index with relation to each other.

With the above and other objects in view, our invention consists inthe construction and novel combinationand arrangement of parts hereinafter fully described, illustrated in the accompanying drawings, and pointed out in the claims hereto appended, it being understood that various changes in the form, proportions, and minor details of construction, within the scope of the claims, may be resorted to without departing fromthe spirit or sacrificing any of the advantages of the invention.

In the drawings:

Figur 1 is a central vertical section through a drum wherein is operatively positioned a liquid fuel vaporizing pot type of burner equipped with the present bafile system;

Fig. 2 is a transverse section through the burner pot, taken just above the bafile structure therein; and

Figs. 3 and 4 are enlarged elevational and perspective views, respectively, each looking toward As herein illustrated, an upright heating drum D carries in its upper region a shell it open at the bottom and at H upon one side thereof, the shell constituting a so-called economizer .which is spaced from the vertical walls 12 of the drum. Near its bottom the drum is provided with a floor i3 and with depending feet M which, when rested upon a building floor, will support the drum slightly elevated whereby air may freely circulate thereunder. In its front wall we provide a lighting door l hinged at the bottom and provided near its top with a handle HS in operative connection with a bolt whereby to secure th door in a normally closed position. A drum of this character is commonly enclosed Within a cabinet (not shown) of ornamental character. Extending from the rear wall of the drum, and in communication with the interior thereof, is a flue pipe i'i leading to a chimney (not shown). The parts just described are more orless conventional at the present time, and have been adverted to mainly because it is with such a construction that the oil burner of our invention may advantageously be used.

The burner unit comprises a cylindrical pot P open at the top where it is provided with an outturned flange adapted to rest upon an angle ring 22 which is affixed to the interior of the drum, as by bolts. The pot thus suspended extends downwardly into the drum, spaced from its vertical walls l2; the pot bottom 23, which may be dished downwardly, is then maintained above the drum floor I3 a distance which is sufficient to permit a ready circulation of air through the intervening space. A substantially level sunken channel 24 may be extended radially in the bottom from about its center to a point at one side of the pot where connection is made with the inlet end of a fuel pipe 25 in communication with a constant level valve 26 to which fuel is fed from a supply source (not shown). By the provision of the channel 24 we obtain the advantage of locating the fuel pipe at the lowest possible point.

Near the burner top is a plurality of relatively large holes 2? inwardly slanted from above and arranged in a row circumferentially of the burner for admitting, a secondary supply of air to the interior of the pot; the primary supply of air thereto is admitted through other holes circumferentially of the pot at lower elevations, five such rows 28., 2.9, 3%, 3| and 32 being shown. The holes in the lowermost row are shown as inwardly slanted from below.

The features which are special to our invention are incorporated within a pot burner P of the general kind just described. These consist of a pair of baffle structure units each made up of semi-annular or segmental plates which may be three in number, designated as A, B, and C, and arranged in tiers vertically spaced from each other. These segmental plates in the two units comprise in each instance two complementary sections a, a, b, b, and c, 0', each extending through substantially 180 so that, when positioned operatively with respect to each other, the sections a, a, b, b and c, c will each extend around within the pot for the full circumference th reof. Although the several baffles are much alike in their constructional features, the one which is lowermost, designated as C, is specifically different from the others and. so will require separate description.

This lowermost baffle C is supported within the pot at a point which is elevated above its bottom 23. For this purpose a plurality of pins 35 are anchored to the vertical walls of the pot and extended radially thereinto for a short distance to provide points of support on which the baffle C may be loosely rested. Each section 0, c of this bafile comprises a plate 36 in the form of a semiannulus (see Fig. 4) having flanges 31 upturned at its opposite ends to lie in substantially diametrical relation; its inner concave edge 38 is shown as rounded upwardly, and its outer convex edge may be arcuately notched at 39 for a slight radial distance at points which are intermediate of a pair of segmental ports 46 each of which extends inwardly from a line concentric with the outer edge of the baffle to a point that is relatively close to its rounded concave edge 38; and four radial walls 4| are struck down from the plate 36 along opposite edges of the two segmental ports 40. These walls 4! which lie in vertical planes constitute part of our improved bafile structure whose operation will be described in detail at a later point.

The intermediate bafiie B comprises a plate 56 in the form of a semi-annulus whose inner concave edge 58 is reinforced by a bead, and whose outer convex edge may be arcuately notched at 59 for a slight radial distance at points which are offset with respect to a segmental port 60 which extends outwardly from a point relatively close to its concave inner edge; a pair of ports 51 one at each end of the plate 56 and opening radially thereupon; and four radial walls 6| along opposite edges of the segmental ports 66 and from the radial edges of the ports 5! as well. The rotative position of the port 60 is vertically misaligned with the segmental ports 40 and 56 of the baffles A and C. The walls 6| which lie in vertical planes constitute part of the improved bafile structure whose operation will be described in detail at a later point.

It will be noted that the three baflles each comprises two similar semi-annular or segmental sections, those of the lowermost baffle 0 being arranged on opposite sides of a common diametric line with their plates 36 engaging the pins 35 to be supported thereby. By reference to Fig. 2 it will be noted that six anchor pins are provided, arranged in two sets of three each symmetrically on opposite sides of the diametric line which separates the two sections 0, c; the positions of these pins are such as to clear the depending radial walls 4 I. The pins 35 provide a means of support for the two bafile units at an elevation such that the two semi-annular plates 36 of the lowermost baffle will lie in a horizontal plane intermediately of the two lowermost circumferential rows of holes 3| and 32 comprised in the primary air supply for the burner pot. To facilitate movement of the two bafiie units into operative position and hold them in correct rotary index a pair of diametrically opposed fins may be affixed to the vertical wall of the burner pot in positions to intervene between the sections, as best shown in Figs. 1 and 2. This index position for the baffle structure requires that the two fins 65 be located at points 180 apart and from the fuel inlet pipe 25; in this position an unported area comprised in the lowermost baffle C will be disposed directly above the point of fuel inlet, and ported areas will be located to the side thereof at substantially equal distances.

Preliminary to insertion of the two baffie units into the burner pot it will be found advantageous to preassemble the three sections a, b, and 0 into one unit, and the three sections a, b, and 0 into a second unit. To do this, each set of three sections is arranged in the superposed relation best shown in Fig. 4 with the feet 53 of the legs 52 depending from the bafiie A inserted through preformed slots in the plates 56 of the baiile B, the feet protruding a 'distance suiiicient to per- Init of their'bein'g turned and clinched opposite sides (see Fig. 3); the feet 63 of the legs 62 depending from the baffle B are likewise inserted through preformed slots in the plates 36 of the baflie C, these feet being also protruded a distance sufiicient to permit of their being turned and clinched on the opposite side. The positions of the slots through which the feet are inserted is such as to predetermine rotative settings of the baffles A and C in mutual alignment and of the intermediate baifie- B in misalignment therewith.

Each unit of three baffle sections is next passed through thedoorway in the front of the drum D to-be placed through the open top of the not into operative position therewithin. As'has already been-explained, the positions of the anon the" of the centralopenings and iof the ports in the chored pins will predetermine the vertical po- 0 sition of the twosections of the lowermost baiiie and thereby theother baiiles which have been previously assembled therewith in unitary relation.- The vertical spacing between the bafiies is such that the semi-annular plates 56 of the baiiie B will lie in a horizontal plane intermediately-of thecircumferential rows of holes 39 and 3!, and the semi-annular plates 45 of the baiile'A-will lie in ahorizontal plane intermediately of the circumferential rows of holes 28 and 2t, -all the holescomprised in these three rows forming a major part of the primary air supply for theburner pot. Because of the staggered rotative-positioning of the three baifies, the segmental ports iifi of the baiiie B will lie oppositely of and directly between unported areas of the-semi-annular plates 38 and t6, and the unported areas of the semi-annular plates 56 will lie oppositely of and directly between the.

segmental ports 40 and Eli. Likewise each pair of open ports 5? in the two semi-annular plates 56 of the intermediate baffle B willoccupy confronting positions so as to constitute in each case a single segmental port similar to the port 60 but staggered with respect to the proximate segmental ports 50 and-4t in the baffles above and below.- The ported and unported areas of the horizontal baffles and the vertical radially disposed-walls thereof provide the tortuous passageway-- composed of vertical and horizontal portions and extending from the bottom to the top of the baffie structure and radially outset from the central vertical passageway.

The outside diameter of the three bafiies is several bafiies'as well as the positioning of these ports with respect to each other; and still another is the provision and disposition of the ra- 1 dial walls depending into the spaces between the baffles at points adjacent the segmental ports therein? "Vihile-satisfactory results may be obtained even when there is variation in these factors to some extent, we have demonstrated that superior performance will be assured with a burner whose pot has an inside diameter of about 11 when the diameter -of-the central opening in the lowermost bafile is about 4 (12.56

.sq. in. "in area)- and the d-iametersof the cen-- tral openings inthe two bafiies thereabove are about 5 23.-7 6---sq. in; in area); when the-- spacing between the lowermost-baffle andthe pot bottom is about 3", when thespacing between thetwo lower baifies is about 1% and the spacing between the two upperbaffles is about 2%"; when -the;unported area of each of the three bafiie plates is about 45 sq. in., the

ported area of the'lowermost baffle-being about 37 sq; in., and the ported area of each of the two upper baiiies being about '26 sq'. i111; and when each radialwall adjacent one edgeof a-segmental 1 port depends therefrom foradistance of about 3/1)! p I It will thus be seen that the-areaof the central opening in the lower-most battle-isapproximately one-half that of'each of theconcentric openings in the baffles thereabova that the spac-- ing between the two lower baffles is approxi- -mately one-half that which-obtains between the two upperbaifies, that the;;ported area of the two upper bafiies is aboutone-halftnat ojits unported area, and thatthe ported area of the is at least 50% greater than that only 15% just one such row as in the case of the lesser spacing between the two lower bafiies. 1 In operation, the burning rate is controlled by the amount of liquid fuel which is supplied; For

a minimum or low fire volumeoifuel, all the; air necessary for combustion below or at the low fire baffle C enters through the lowest row of very slightly-less than the inside of the burner i baiiie (on bailies segmental notch (or notches) in an adjacent Q gr gipl esi e a s b e primary air holes 32. At this stage the low fire baffle Q serves to halt part of the down drafts from the'upperportion of the pot which tend to disturb the balance of combustion in the space below this baflie.

Asa consequence, a low flame may be maintained under such conditions with a m ni u e gi ee arbe In previous baffle systems ithas been common to control the down draft air eddies in the burner ,pot by solid low fire baflies each having a single ,central opening therethrough for escape of the an upwardly slanted flange ring consisting oii two 'coa cting semi-circular, separable segments 66 and 6'5, is fitted to the burner pot upon its from one level to the 16' to an area of desired size.

flame and combustionproducts, or having .ripheral perforations or notchesfor this purpose. rBaffie arrangementsof these kinds'have the dis- I advantagethat sharp, changes in the flame shape are produced, tending to upset the combustion bafiies have also been suggested, but these require next Stepped or staggered spacing which is too far apart, and also allow too much circulation in the pot for the maintenance of a good low fire. Placing of the top bafiles closer together, as herein described, causes the high fire rate to be lowered or choked off before sufficient control is obtained of the air eddies; we find it expedient, therefore, to use the downturned radial walls adjacent the ported areas of the baffles to control the amount of fuel vapor which tends to ascend therethrough. A fixed distance is maintained between the baffles by the legs depending from the radial walls for connection with the next lower bafile. The baffle structure in its entirety is suspended vertically in spaced relation to the burner bottom 23 and above the lowermost primary air inlets 32, as by means of supporting pins 35 which are anchored to the burner walls. The bafile assemblies are held in rotary index with the fuel inlet pipe 25 by the vertical spacing fins 65. It is important for low fire operation that the lowermost baille C be so positioned rotatively that an unported area of its body be located over the inlet point of the oil supply. The term ported area, wherever used, refers to the area of one or more of the ports 40, D, 51, and iii), and has no reference to the vertical passageway through the system formed by the central openings of the baffles.

In normal operation, oil is fed through the control valve and fuel line into the burner at a point adjacent its bottom. Upon ignition, the flame burns from the surface of the oil pool on the bottom until the rate of generation of fuel vapor increases to the point that burning directly from the pool surface is prevented by reason of an increased enrichment of the oil vapor. The flame then rises above the burner bottom 23, and generation of the fuel vapor is then produced from the heat reflected from the flame above. Combustion continues at a rate which is commen- .surate with the feed of oil into the burner, and so long as the rate of oil feed is kept below certain limits, or in proper relation to the supply of air entering through the lowermost inlet holes 32, the base of the flame will stay below the lower baffle C. When more fuel is added, the base flame will then rise to the higher rows of air inlet holes because the volume of the rich mixture of oil vapor and air in the lower portion of the burner has then increased substantially. When high fire has been reached, the flame base is at the level of the row of secondary air inlet holes 2'1, and while at this point the rate of fuel admitted into the burner can be increased until the flame starts to smoke. At this point maximum capacity will have been reached.

As the flame leaves the burner through the center aperture of the flame ring at the top, it radiates heat to the side walls of the drum D. The flame and hot gases will also enter the economizer ll! through its open bottom to impinge the top of the heat drum and then leave the economizer through the lateral opening 1 i at the front thereof for circulation in the surrounding space interiorly of the heat drum D. Eventually the hot gases will discharge into the chimney through the flue passage ll. Because of this manner of operation the flame and hot gases are forced to give up their heat.

If it becomes necessary or desirable to clean out Or repair the burner, each unit of the baffle structure may be independently removed through the lighting door l5 at the front of the drum. This is true even though the diameter of each baffle unit be larger than the door opening, due to each unit comprising but one of the two sections of the several baffles. This is a marked advantage because it permits use of a smaller combustion door than would otherwise be required, thereby obviating the tendency of a larger door to warp and produce leaks with consequent reduction in the efficiency of the heater.

We claim:

1. In combination with a pot-type burner having means for supplying thereto liquid fuel in a controlled amount, the burner wall being cylindrical and provided with primary air inlet holes arranged in a plurality of circumferential rows, a system of interconnected superposed horizontal baffles in the burner, spaced apart vertically to position each bafile between two rows of inlet holes, each bafile having a central opening to define a vertical passageway through the system, said horizontal baffles being provided with openings and having vertical walls located at opposite edges of the openings and disposed transversely of the baffles, the openings of said baffles forming ported areas, the openings in each baflle :eing staggered vertically with respect to the openings of adjacent baffles, and the area of the central opening in the lowermost baffle being approximately one-half that in the baiiie next above.

2. In combination with a pot-type burner having means for supplying thereto liquid fuel in a controlled amount, the burner wall being cylinrical and provided with primary air inlet holes arranged in a plurality of circumferential rows, a system of interconnected superposed horizontal baffles in the burner, spaced apart vertically to position each bafile between two rows of inlet holes, each baffle having a central opening to define a vertical passageway through the system, said horizontal baffles being provided with openings and having vertical walls located at opposite edges of the openings and disposed transversely of the bafiies, the openings of said bafiles forming ported areas, the openings in each baffle being staggered vertically with respect to the openings or adjacent bafiies, and the ported area of the lowermost baflie being greater by at least fifty per cent than the ported area of the baffle next above.

3. In combination with a pot-type burner having means for supplying thereto liquid fuel in a controlled amount, the burner wall being cylindrical and provided with primary air inlet holes arranged in plural circumferential rows, a system of three interconnected superposed baflies in the burner, spaced apart vertically to position each baffle between two rows of inlet holes, each bafile having a central opening to define a vertical passageway through the system, the area of the central opening of the lowermost bafile being approximately one-half that in each of the others thereabove.

4. In combination with a pot-type burner having means for supplying thereto liquid fuel in a controlled amount, the burner wall being provided with primary air inlet holes arranged in a plurality of circumferential rows, a system of interconnected superposed bafiles in the burner, spaced apart vertically to position each baffle between two rows of inlet holes, each baffle having a central opening to define a vertical passageway through the system, the area of the central opening in the lowermost bafile being approximately one-half that in the baffle next above and said baffles having openings forming ported areas staggered vertically with respect to one another and forming tortuous passageways spaced from the central passageway.

5. In combination with a pot-type burner having means for supplying thereto liquid fuel in a controlled amount, the burner wall being provided with primary air inlet holes arranged in a plurality of circumferential rows, a baflle structure comprising a plurality of interconnected superposed bafiles in the burner, spaced apart vertically to position each bafile between two rows of inlet holes, each bafiie having a central opening to define a vertical passageway through the structure, said bafiles having openings forming ported areas and staggered vertically with respect to one another and forming tortuous passageways spaced radially from the central passageway, the ported area of the lowermost bafile being substantially greater than the ported area of the baiiie next above and the ported area of the next to the lowermost baflle being substantially less than its total area, said structure consisting of two complementary units separated vertically in H a plane diametrically of the burner, each unit being movable independently into and out of the burner.

6. In combination with a pot-type burner having means for supplying thereto liquid fuel in a controlled amount, the burner wall being provided with primary air inlet holes arranged in a plurality of circumferential rows, a system of interconnected superposed baffles in the burner, at least three in number, spaced apart vertically to position each bafiie between two rows of inlet holes, each baffle having a central opening to define a vertical passageway through the system and the area of the central opening in the lowermost baffle being approximately one-half that in each of the others thereabove, said bafiles having other openings forming ported areas and staggered vertically with respect to one another and forming tortuous passageways spaced radially from the central passageway.

7. In combination with a pot-type burner having means for supplying thereto liquid fuel in a controlled amount, the burner wall being provided with primary air inlet holes arranged in a plurality of circumferential rows, a baiile structure in the burner comprising interconnected superposed baffles, at least three in number, spaced apart vertically to position each bafiie between two rows of inlet holes, each baflle having a central opening to define a vertical passageway through the structure and the area of the central opening in the lowermost baffle being sub stantially less than that of each of the others thereabove, bafiies having other openings staggered vertically with respect to one another and forming ported areas and providing tortuous passageways spaced radially from the central passageway, said baffle structure consisting of two complementary units separated vertically in a plane diametrically of the burner, each unit being independently movable into and out of the burner.

8. In combination with a pot-type burner having means for supplying thereto liquid fuel in a controlled amount, the burner wall being provided with primary air inlets arranged in plural circumferential rows, a system of three interconnected superposed annular baffles in the burner, spaced apart vertically to position each baflle between two rows of inlet holes and provided with aligned central openings defining a vertical passageway, said bafiles being provided with staggered openings forming ported areas and each baffle having a plurality of said ported areas vertically staggered with respect to those in the next adjacent baflle forming a tortuous passageway spaced radially from the central vertical passageway, and means adjacent the ported areas of the baffles for retarding movement of vapors ascending through the bafrle system, the distance between the two lowermost bafiles being approximately one-half the distance between the two upper baffles.

9. In combination with a pot-type burner having means for supplying thereto liquid fuel in a controlled amount, the burner wall being provided with primary air inlet holes arranged in a plurality of circumferential rows, a system of superposed annular baflles in the burner, spaced apart vertically to position each bafiie between two rows of inlet holes and rovided with central aligned openings forming a central vertical passageway, said bafiles being provided with staggered openings forming ported areas and each bafiie having a plurality of said ported areas vertically staggered with respect to those in the next adjacent bafiie, and radially extending walls depending from each baffle at points adjacent opposite sides of the ported areas, the openings and the radial walls forming tortuous passageways composed of vertical and horizontal portions and spaced from the central vertical passageway the distance between the two lowermost baffles being approximately one-half the distance between the two uppermost baflles.

10. In combination with a pot type burner having means for supplying thereto liquid fuel in a controlled amount, the burner wall being provided with primary air inlet holes arranged in a plurality of circumferential rows, a system of superposed annular baffles in the burner, spaced apart vertically to position each bafile between two rows of inlet holes and provided with central aligned openings forming a central vertical passageway, said baiiles being provided with staggered openings forming orted areas and each bafile having a plurality of said ported areas vertically staggered with respect to those in the next adjacent bafiie, and radially extending walls depending from each baffle at points adjacent opposite sides of the ported areas, the openings and the radial walls forming tortuous passageways composed of vertical and horizontal portions and spaced from the central vertical passageway, said baffles being three in number, the distance between the lower baffles being approximately one-half the distance between the two upper baffles, and the depending distance of the radial walls being less than half the spacing between the two upper baiiies and more than half the spacing between the two lower bafdes.

KENNETH S. JENSON.

FREDERICK W. SUI-IR.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,204,694 Piehl June 18, 1940 2,231,151 Breese Feb. 11, 1941 2,241,470 Miller May 13, 1941 2,244,766 Cooper June 10, 1941 2,258,679 Hayter Oct. 14, 1941 2,260,839 Miller et al Oct. 28, 1941 2,339,637 Hayter Jan. 18, 1944 2,422,209 Reeves et a1 June 17, 1947 

